Electroplating apparatus



y 1958 M. B. HAMMOND ET L 2,833,708

ELECTROPLATING APPARATUS Filed May 5, 1955 2 Sheets-Sheet 1 46 |sP 4s 5INVENTORS.

. Milton 5. Hammond Fl 2 BY Glade B. Bowman THE/R ATTOR/VE Y5 May 6,1958 M. B. HAMMOND ET AL 2,833,708

ELECTROPLATING APPARATUS 3 Filed May 5, 1955 .2 Sheets-Sheet 2 Milton 5.Hammond F 4 BY Glade B. Bowman THE /R A TTOR/VE Y5 ELECTROPLATINGAPPARATUS Milton l3. Hammond and Glade B. Bowman, Edgeworth, Pa.,assignors to Rockwell Spring and Axle Company, Coraopolis, Pa., acorporation of Pennsylvania Application May 5, 1955, Serial No. 506,338

9 Claims. (Cl. 204-222) This invention relates to a method and apparatusfor uniformly electroplating somewhat complex articles of non-uniformcurvature and surface, as contrasted with geometrically simpler articleswith their uniform and regular surfaces, such as fiatrecording discs,cylinders, and similar articles of revolution or at least articlespredominantly annular and/or flat of form.

The invention finds particular application to the plating of automobilebumpers, but is useful, in the broad sense, in other applications notlimited to bumpers, for instance, cylinders, discs, or curved shellstructures. According to a feature of the invention, the article to beplated, of which a bumper is a good example, is subjected to highphysical agitation in a plating bath whereby-the immersed surfacesthereof impinge against the liquid of the bath in a progressivelychanging direction at which, during'some phase of the operation, theimpingement is directly or approximately at right angles to each andevery portion of the surface to be plated. The bumper or other articlein its progress through the bath describes a path which is conducive touniform plating, but in which the article is practically continuallychanging its general relationship to or distance from the platinganodes, or else changing both relationship and distance thereto.

Various features, objects, and advantages will either be specificallypointed out or become apparent when, for a better understanding of theinvention, reference is made to the following description taken inconjunction with the accompanying drawings in which:

Figure l is a plan view of an electrolyte tank type article platingapparatus according to the invention presently disclosed;

Figure 2 is a side sectional elevation based on Figure 1' along thesection lines II-II so that the showing of Figure 3 is removed;

Figure 3 is a rear elevational view along the lines III-III of Figure 1;

Figure 4 is an end elevational view along the lines IV-IV of Figure l;and

Figure 5 is a visual aid diagrammatically approximatingthethree-dimensional motion of agitation of the articles undergoing platingin the apparatus.

Referring more particularly to the accompanying drawings, in Figures 1-4an upwardly open plating tank adaptedto contain an electrolyte is shownhaving front and rear walls and 12,21 rectangularly shaped, horizontallydisposed bottom 13 supported at the four corners by means of a set ofblocks 15, and a set of opposite end walls 14 and 16, each of which isprovided with a transverse outwardly extending flat flange 18 along itsupper edge. Adapted to be immersed in the electrolyte within the tank,the level of which is indicated at 21), there are provided a first and asecond row of generally cylindrical bagged anodes forming a frontplurality of electrodes 22 and a rear plurality of electrodes 24. Theelectrodes 22, 24, whichwere of nickel in one physically constructedembodiment of the invention,- areeach provided with a hook 26 at theirupper ends with which they are 's'us pended from the respectivegenerally parallel opposite legs of a U-shaped anodic bus bar 28. Thebus bar 28 is adapted to be appropriately connected, as by means of aheavy woven copper cable 30, to a source of positive electricalpotential (not shown). Through the medium or" the electrolyte, thenickel or other'metal from the cylindrically shaped anodes 22, 24 istransferred to the exposed surface of an article to be plated which maybe in the form of a steel bumper 32 which is drawn, by die forming orotherwise, into a shell of substantially U- shaped transverse crosssection and which is bent at a point along its length so as to besubstantially v shaped or U- shaped in over-all appearance between itsopposite ends. The bumper 32 is formed with suitable tabs or aperturesadjacent the concave side thereof to which any one of three or morevertically spaced apart cross members -34 may be detachably fastened,the cross members being fast to a common hook-carrying hanger 36 whichis hooked onto and depends from a horizontally disposed cathode bus bar33 of rectangular cross section. A set of clamps (not shown) may beprovided'to secure the hooked end of the hanger 36 securely to the busbar 38. A number of these hangers 36 and a plurality of bumpers of acorresponding multiple of that number carried thereby may be secured todepend from the cathode b'us bar 38 in axially spaced positions from thelatter. At the opposite ends of the tank outside its end walls 14 and16, there is provided a pair of vertically disposed and parallel splinedshafts 40 having disc-shaped plate 42, 44 at the head or upper endthereof. The head discs 42, 44 are identical to one another and, in theinterests of brevity, only the head 44 will be particularly described asfollows.

The head 44 is rotatably and axially fast to its coin panion shaft {itand adapted to rotate concentrically ther with about a common axis 46.At an eccentric location in the head 44 relative to the axis 46, a pivot.pin 48 is provided having an upper end threadably received in arectangular block of metal 50 and having its lower end depending throughan opening in the head 44 and secured thereto as by means of a cotterpin 52. The metal block 50 has a rectangularly shaped through boretherein, Figure 4, which is complemental to and receives the rectangularly cross-sectioned cathode bus bar 38 therewithin and has athumbscrew 54 for holding the bus bar 38 axially fast to the metal block50.

At the end portion of the bus bar 38 adjacent the metal= lic block 50, awoven flexible copper wire cable 56 is secured, as by means of a set ofscrews 58, to the bus bar in electrically conducting relationship forreceiving cathodic current therefrom and transmitting it to a source ofelectrical power to which the anode cable 30 is connected. I,

In one physically constructed embodiment of the invention, theelectrical pressure or potential difference maintained between the busbars 28 and 38 was approximately 9 /2 volts D. C. The end of the cathodebus bar 38 opposite to the portion to which the cable 56 is eonnected issimilarly supported and connected to the head 42. The parallel splinedshafts 40 have their respective mid-portions received in and passedthrough a complementally splined hub portion of a set of driven oroutput sprockets 60 and 62. In the interests of brevity, only thesprocket 60 will be hereinafter described.- The sprocket 60 is supportedbetween a pair of vertically spaced apart plates 64 secured, as by meansof a bracket and a set of fasteners as at 66, to one ofthe two oppositeend flanges at the upper ends of the opposite end walls 14 and 16 of theplating tank. The s'plined connection between the sprocket 60, havingteeth receivable in a drive chain, and the shaft 40 therethrough is suchthat the shaft isrotatably fast but axially slid-able with relation. to.the sprocket 60.. The sprocket 60 is prevented from axial travelbymeans, of the spaced apart plate 64, but the shaft 40 has freedom ofmotion in two directions, notably axially and rotatably about its axis46. Another sprocket of somewhat smaller diameter than the sprockets60and 62, isprovided at 68which serves as a drive sprocket in a mannerhereinafter described and five similarly small idlersprockets areprovided at the four corner positions of the tank at 70 and at 72 on theopposite or front side of the tank from the drive sprocket 68.

Drive transmitting means as follows is provided for coordinating themotion of the shafts 40 as they rotate about their separate axes. A linkchain 74 is trained over the respective drivesprocket 68, drivensprockets 60 and 62, and idler sprockets 70 and 72, and at all timesexactly coordinates the movement of the heads 42, 44 and the oppositeends of the cathode bus bar 38 such that the attitude of the bus bar isalways parallel to the front and rear walls and 12 of the rectangularlyshaped electroplating tank. This feature of parallelism accounts for oneof several reasons why the cable 56 onthe bus bar has no tendency towind up and kink and twist in the present apparatus.

The lower end portion of each of the shafts 40 includes auction ofsmooth circumference as at 76 which at its lower extremity rigidlycarries a transversely disposed circular thrust disk 80 received withina shallow cupshaped recess formed in the head of a reciprocatingcylindrical piston 82 of metal, preferably brass. An interposed ballthrust bearing 84 is received on the floor of the cup-shaped recess andsupports the disk 80 and the shaft 40 so as to permit relative rotationbetween 'the shaft 40 and the piston 82, at the same time holding theshaft 40 and the reciprocating piston 82 in an accurately spaced apartrelationship for coordinated axial motion as the piston lifts the shafton its upward stroke and the shaft thereupon follows the piston undergravity as the piston returns on its downward stroke of reciprocation.The cylindrical or cup-shaped recess in the head of the piston 82contains a suitable quantity of lubricant so as to lubricate theantifriction thrust bearing in which the thrust disk 80 on the extremityof the shaft is journaled. A pin passing through the opposite sides of agenerally flat milled portion adjacent the base of the piston 82pivotally carries a pair of short depending links 86 which at theirswinging lower ends are formed with a pair of registering aperturesreceiving therewithin another pin 88. The lower pin 88 extendstransversely through a bore formed in one end of a rectangularlycross-sectioned walking beam or lever 92. The end wall 16 of the platingtank carries a hollow cylindrical bearing or guide 90 secured thereto bymeans of a suitable bracket and receiving and guiding therewithin thereciprocating piston 82 which is preferably kept coated with grease. Atits mid-portion between the opposite ends, the beam 92 is pivoted at 94to the end wall 16 of the plating tank for rocking movement about thepivot 94 as a center. At its opposite end the walking beam 92 isprovided with an elongated pin receiving slot 96. The stationarypositionof the pivot 94 prevents the rectangularly crosssectioned beam 92 frommoving out of its own plane, and accordingly, the pin and linkconnection 88, 86 at one end of the beam satisfactorily prevents theshaft receiving piston 82 from rotating with theshaft 40.

Drive transmitting means as ,follows is provided for coordinating motionof the shafts 40 axially in unison. A piece offline shafting 98 isjournaled in a pair of spaced apart sleevebearings 100 for rotationalong its axis 102 and the bearings 100 are secured to the lower surfaceportion of the rear wall 12 of the plating tank. At its oppositeextremities, the line shafting 98 has a pair of disks 104 rotatably andaxially fast thereto and each of which carries a pin 106 disposedeccentrically to the outer face thereof and passing through theelongated slot 96 in the adjacent walking beam 92. The pins 106 areaxially aligned at all times 'with one another and each has a retainingcollar 108 preventing its withdrawal from the slot 96 in which the pinis received. Rotation of the line shafting 98 about its axis 102 causescoordinated motion of the end discs 104 and the mutually alignedeccentric pins 106 which results in imparting an oscillating movement tothe walking beams 92 and a reciprocatory movement of substantiallysimple harmonic motion to the shafts 40 in unison along their axes 46.Upon rotation of the discs 104, the walking beams will oscillate betweenthefull line position and the dotted line position 92a, Figure 4, with aresulting amount of vertical travel at the shaft end as indicated at110, Figure 4. In addition to the vertical travel of a magnitudecorresponding to the dimension 110, the shafts 40 are capable ofsuccessive and continued rotation through their full 360 degrees of areas determined by the position of thecompanion driven or output pulleys60, 62. The coordination in phase between the shafts 40 as theyreciprocate upwardly and downwardly together results in the fact thatthe attitude of the bus bar 38 is always such that it is parallel to thehorizontal bottom 13 of the tank. This feaure of parallelism accountsfor another of several reasons why the cable 56 on the bar 38 has notendency to wind up or knot during sustained operation of the presentapparatus.

Separate power means are provided for driving the shaft rotating chain74 and for driving the line shafting 98. An illustrative example of oneof the power means is a reversible electric motor 112 which is connectedby means of a combined fluid coupling and reduction spur gear component114 to the drive pulley 68 for the chain 74. The reversible motor 112 isof well-known electrically double wound rotor construction whoserespective windings are selectively connectable at will to a powersource as at 116 as by means of a double throw switch 118. Thedoublethrow switch 118 is movable from a neutral position in which neitherrotor winding is energized into opposite positions for energizing one orthe other windings of the rotor so as to drive the drive sprocket 68 inone direction or the other as desired.

Illustrative of the other power means is an electric motor 120 which ismechanically connected through a reduction gear box 122 to the lineshafting 98 at the mid as follows.

portion of the latter. The motor is arranged to be electricallyconnected to a source of electrical power 124 through a single throwmanual switch 126 which is operator operable. The direction of rotationof the motor 120 is a matter of design choice, and is not selectable bythe operator inasmuch as the line shafting 98 imparts the same simplereciprocatory motion to the end shafts 40 regardless of which way theline shfting 98 is rotated.

The following is given as an example of the cyclical frequency ofoscillation of the shafts 40 axially and in a direction about their axes46:

' Cycles per minute Axial frequency of cycle 5-60 Rotative frequency ofcycling 5-60 Normal axial frequency 30 Normal rotative frequency 36Operation of the high agitation plating apparatus under control of themanual switches 118, 126 is accomplished timers,'not shown, the doublethrow switch 118 is maintained in one operating position for a period offrom a few seconds to several minutes and then maintained in theopposite operating position for a similar period with the result ofcirculating the bumpers 32 in circular paths in sequentially oppositedirections. Simultaneously therewith, the single throw switch 126 may becontrolled by means of an electrical timer, not shown, so as to closeand compound the circular motion with the substantially simple harmonicmotionof reciprocation of the shafts and heads 40, 42,'and 44 whichimparts a three-dimensional motion tothe bumpers 32 being plated. Incer- By means of manual control or electrical 'tain instances of platingparticular articles, an-automatic cycling operation has been used toadvantage wherein the single throw switch 126 is held closed for-twentyseconds and held open for twenty seconds, with the result that theplated articles are alternately subjected to three-dimensional motionand two-dimensional motion, even though the reversibility of the chain'74 in the latter sense actually provides for opposite directions ofrotation in the single plane providing the two directions of motion. Theinterspersing of periods of the three-dimensional motion described,among the two-dimensional motion periods, has been found to beparticularly effective in the bumper plating field in which theintricate surface of the bumper, due to the varying radii of curvatureof its developed exterior, is otherwise 'di ffic'ult to plate uniformly.

In Figure 5, the diagrammatic two-dimensional path of motion representedwill be an aid to the visualization of the actual three-dimensional pathof motion described by the bumpers during a portion of .the operation ofthe preceding paragraph. Figure represents the path of article motionviewed from the position of the anodes 22 of Figure 2, it being observedthat the bumpers do not rotate as they bodily orbit nor do they revolveabout a rotational axis in any sense, but retain their original positionof orientation in a horizontal plane in much the same manner as thecathode bus bar 38, which, as already noted, -maintains its relation ofparallelism to "the front, bottom, and rear Walls of the plating tankeven though it is being oscillated with a compound motion. Through theflatter portions of the path of the bumper as indicated at 128 and 130,the bumper is moving transversely of the anodes 22, whereas in the morecurved portions 132, 134 of the path of travel, the bumper is movingrespectively toward and from one row of electrodes 22 and from andtoward the other row of electrodes 24. Simultaneously, the vector ofmotion of the bumpers in the more curved portions 132, 134 has apronounced component lengthwise of the depending electrodes. Inasmuch asany motion of reciprocation is subject to a dwell phase and to a maximumvelocity phase in each cycle, the transverse movement of the bumpersalong the path portions 128 and 130 is relatively free of up and downtravel of the bumpers, whereas the motion of approach and separation ofthe bumpers at 132, 134 relative to the anodes is accompanied by arather pronounced up and down component of motion thereof. In view ofthe constant angular rotation of the heads 42, 44 compared to theirconstantly varying velocity of axial travel and in view of the fact thatthe cyclic frequency of reciprocation is slightly at variance with, andpreferably slower than, the rotative frequency, it will readily beappreciated that the opposed convex surfaces to be plated on the bumpers32 undergo such widely varying directions of motion with respect to thefluid against which they impinge that at one time or another eachportion of the surface to be plated is impinging directly at rightangles against the electrolyte fluid. The resulting coating ofelectroplated nickel has been observed to attain a very desirableuniformity of.

thickness about the article to be plated and the results have been foundvery satisfactory in practice.

While we have described certain presently preferred embodiments of ourinvention, it is to be understood that it may be otherwise embodiedwithin the scope of the following claims.

We claim:

1. Apparatus for electroplating a three-dimensional article havingconvex surfaces comprising a tank for fluid in which the article is tobe immersed, a member thereon adapted to suspend the article in thefluid and having means for conducting current therefrom, rows ofelongated electrodes defining an unobstructed open space in the tank,spaced apart means for moving the member and the suspended articlethrough a curved path oscillating so as to weave between the electroderows to continually reverse direction with respect thereto and to thelength of the tank to constantly change the di'stancebee: tween thearticle andthe electrodes, saidmemberhaving opposite end structuresdisposed one over each of said means, connections supporting each endstructure with a rotating fit upon the means at that end for motion in apath closing on itself, and thrust delivery means, for applying thrustto shiftably operate said spaced apart means for moving the member andthe suspendedarti'cle in reciprocatory motion in a directionperpendicular to the plane of rotation aforesaid, said meansconstituting the sole means of support of said member. I I

2. In apparatus for electroplating an article, having convex surfaces, acathode member adapted to suspend the article and having means forconducting current there from, rows of elongated electrodes anod'icallycooperating therewith and defining an unobstructed open 'spa'ce'forreceiving the article therebetween, spaced apart reversible means formoving the member and the-suspended article in either of two directionsthrough a curved path oscillating to and fro in the tank andcontinuously weaving-between the electrode rows so as to cyclically varythe motion and constantly change the distance between the article andthe electrodes, said member having opposite end structures disposed oneover each of said means, connections supporting each end structure witha rotating fit upon the means at that end for motion in a path closingon itself, and thrust delivery means for applying thrust to shiftablyoperate said spaced apart means for moving the member and the suspendedarticle in substantially simple harmonic motion in a directionperpendicular to the plane of rotation aforesaid, said meansconstituting the sole means of support of said member.

3. In a means for electroplating three-dimensional drawn articles, a barmember from which the articles are adapted to be suspended, disc means,said bar member having at least one end structure disposed over saiddisc means, a connection comprising crank pin means supporting said oneend structure with a rotating fit upon said disc means at that end forswinging motion in a path closing on itself, operator controlled meanswhereby the disc means is rotated in either direction, and separateoperator controlled means for raising and lowering the disc meansindependently of the control of the disc rotating means, said meansconstituting the sole means of support for said bar member.

4. In combination, a bar member from which articles to be electroplatedare adapted to be suspended, a pair of spaced apart discs disposed onebelow each end structure of the bar member, connections including crankpin means supporting each end structure With a rotating fit on the discat that end for swinging motion in a path closing on itself, operatorcontrolled means whereby the discs are rotated in the same one sensetogether or in the opposite sense together, and separate operatorcontrolled means for raising and lowering the pair of discssimultaneously but independently of the control of the disc rotatingmeans, said means constituting the sole means of support for said barmember.

5. In means for electroplating articles, a cathode bar from which thearticles are to be h ng, a plurality of horizontally spaced apart headsby which spaced portions of the bar are individually eccentricallymounted and supported, a vertical rotatable support shaft connected toeach head in driving relationship thereto for imparting eccentric motionof oscillation to the cathode bar,*and means for moving the shafts inunison axially and in a direction about their axes.

6. In means for electroplating articles, a bus bar from which thearticles are to be hung, horizontally spaced apart discs by which theopposite ends of the bus bar are supported and eccentrically mounted, avertical rotatable support shaft connected to each disc in drivingrelation ship thereto for imparting eccentric oscillation to the busbar, means having an eccentric rocking action for moving each of theshafts axially in unison with the other shaft,

, 7 and separate ghavingta splined connection to each shaft-for rotatingit about its own axis in synchronism with the other shaft. A p r7.-Mechanism for high agitation electroplating of articles comprising aplurality of upstanding splined sup port shafts disposed in parallelismto one another, a like number of coplanar heads supported thereby andeach ticles comprising a plurality of splined vertical shafts,

Il -like number of.cop lanar plates fast'thereto and eachhayinganupstandingeccentrically located pin in the facethereofiacathodelbus means pivotally carriedby the pins in common,drivesprocket means splined to the shafts, 20

eccentricallyt driven walking beam means connected to said; shafts forshifting them axially, a common chain coordinating the drive sprocketmeans for rotating the shafts in unisonQand means including common lineshafting and eccentric means connected to the walking beam meansforshifting, the shafts axially in unison.

9 For use with a plating tank provided with horizontal bar means andsuspension members hanging therefrom downwardly into the tank forsupporting articles with curving surfaces to be plated, electrical cablemeans secured to the bar means for conducting plating current, supportmeans connected to the bar means for simultaneously producing motionhaving a vertical component, a horizontal component in the plane of thevertical component, and a horizontal component in a plane perpendicularto the vertical component and to the first said horizontal component,all in a curving path closing on itself in a manner to prevent kinkingof the cable means,

said support means comprising eccentrically mounted means supportingthebar means at opposite ends and mounted for vertical movement and forrotation in horizontal planes, and power means for driving theeccentrics both ways. I

References Cited in the file of this patent UNITED STATES PATENTS

1. APPARATUS FOR ELECTROPLATING A THREE-DIMENSIONAL ARTICLE HAVINGCONVEX SURFACES COMPRISING A TANK FOR FLUID IN WHICH THE ARTICLE IS TOBE IMMERSED, A MEMBER THEREON ADAPTED TO SUSPEND THE ARTICLE IN THEFLUID AND HAVING MEANS FOR CONDUCTING CURRENT THEREFROM, ROWS OFELONGATED ELECTRODES DEFINING AN UNOBSTRUCTED OPEN SPACE IN THE TANK,SPACED APART MEANS FOR MOVING THE MEMBER AND THE SUSPENDED ARTICLETHROUGH A CURVED PATH OSCILLATING SO AS TO WEAVE BETWEEN THE ELECTRODEROWS TO CONTINUALLY REVERSE DIRECTION WITH RESPECT THERETO AND TO THELENGTH OF THE TANK OF CONSTANTLY CHANGE THE DISTANCE BETWEEN THE ARTICLEAND THE ELECTRODES, SAID MEMBER HAVING OPPOSITE END STRUCTURES DISPOSEDONE OVER EACH OF SAID MEANS, CONNECTIONS SUPPORTING EACH END STRUCTUREWITH A ROTATING FIT UPON THE MEANS AT THAT END FOR MOTION IN A PATHCLOSING ON ITSELF, AND THRUST DELIVERY MEANS FOR APPLYING THRUST TOSHIFTABLY OPERATE SAID SPACED APART MEANS FOR MOVING THE MEMBER AND THESUSPENDED ARTICLE IN RECIPROCATORY MOTION IN A DIRECTION PERPENDICULARTO THE PLANE OF ROTATION AFORESAID, SAID MEANS CONSTITUTING THE SOLEMEANS OF SUPPORT OF SAID MEMBER.